I select my core and then it asks me to log in. I enter my details and then if hands me back to Roon but asks me to log in again. I have been using Roon for a long tome and this is the first time I have experienced this problem.
Roon Core Platform
Linux (NAS/SonicTransporter/Antipodes/Ubuntu/etc.)
I just experienced the same issue, very infuriating.
I tried reinstalling my Core, removed all active Roon sessions, restarted the PC running Core etc.
The fix (at least for me) was to re-establish my DSL connection. After my router established a new DSL connection, it finally let me through the login screen.
So, having uninstalled and re-installed Roon, more than once - a sign of madness surely - I managed to login from a different computer with Roon installed and that did the trick. I wouldn’t not say it was a solution as I am not really sure why it worked. I thought Roon themselves may know why, or at least have some suggestions. Anyway, it’s working.